1. Field of the Invention
The invention is related to the field of magnetic disk drive systems and, in particular, to fabricating write heads with a write pole electronic lapping guide and a trailing shield electronic lapping guide.
2. Statement of the Problem
Magnetic disk drive systems typically include a magnetic disk, a recording head having write and read elements, a suspension arm, and an actuator arm. As the magnetic disk is rotated, air adjacent to the disk surface moves with the disk. This allows the recording head (also referred to as a slider) to fly on an extremely thin cushion of air, generally referred to as an air bearing. When the recording head flies on the air bearing, the actuator arm swings the suspension arm to place the recording head over selected circular tracks on the rotating magnetic disk where signal fields are written to and read by the write and read elements, respectively. The write and read elements are connected to processing circuitry that operates according to a computer program to implement write and read functions.
Write heads and other components of the recording heads are typically produced using thin-film deposition and patterning techniques. The several material layers which make up a write head for a magnetic recording head are typically formed by depositing full film materials of the write pole layers on a wafer substrate, depositing and patterning a masking layer over the write pole layers to form a mask structure, etching the exposed portion of the write pole layers around the mask structure, and then removing the mask structure. A trailing shield structure may then be formed around the write pole. The trailing shield is formed to prevent the write pole from writing to neighboring tracks during the writing process.
After the recording heads are formed, the recording heads are cut from the wafer into individual recording heads, or rows of recording heads. Sawing has been a typical method for separating wafers into individual recording heads. The surfaces of the recording heads that are exposed when the wafers are cut eventually form the air bearing surface (ABS) of the recording head.
A lapping process is used to form the ABS of a recording head, and more particularly, the ABS of the write head. To monitor progress of the lapping process, electronic lapping guides (ELGs) are often formed proximate to a write pole. FIG. 1 illustrates a prior art write pole portion of a write head 100 with an ELG 140. The write head 100 includes a write pole 110 and a yoke 120. The location where write pole 110 flares out to become yoke 120 is known as the flare point 125. A trailing shield 130 envelopes portions of write pole 110 (which are not visible in FIG. 1). A lapping process is used to lap trailing shield 130 and write pole 110 to form ABS 150. The lapping process is performed from the bottom up in FIG. 1.
A resistance of ELG 140 is used to measure a throat height 165, which is the distance between ABS 150 and a back edge 132 of trailing shield 130. A back edge 142 of ELG 140 is aligned with back edge 132 of trailing shield 130. Current is applied to ELG 140 to measure the resistance of ELG 140. As portions of ELG 140 are lapped away, the resistance of ELG 140 increases. The resistance of ELG 140 correlates with the height of ELG 140, which correlates with throat height 165 of write pole 110. Once the desired throat height 165 is reached, the lapping process is stopped and ABS 150 is completed.
Due to the large density of data recording on magnetic recording devices, it is very important that write heads are fabricated within desired specifications. It is important that a write head 100 have not only a specific throat height 165, but also a specific flare point distance 160. Flare point distance 160 is the distance between ABS 150 and flare point 125. However, present ELGs do not provide a measurement of flare point distance 160, and thus, flare point distance 160 may only be estimated using optical processes, or time consuming TEM metrology.
Further, present ELGs do not provide the ability to gather information from more than one layer of a write head. For instance, if ELG 140 is comprised of a material similar to write pole 110, then measurement equipment attached to ELG 140 gathers information regarding write pole 110, but does not gather precise information regarding trailing shield 130, which is a different layer of material. Thus, it is evident from the above discussion that improved solutions are needed for monitoring a lapping process of an ABS of a write head.